Abstract

Passive AlGaAs waveguides have been shown to be suitable for ultrafast all-optical switching when used at wavelengths in the vicinity of the half-bandgap (around 1.5-1.7 μm).^1,2 Nonlinear phase shifts in excess of π radians have also been observed directly by monitoring self-phase modulation induced spectral broadening of pulses propagating through straight waveguides.^3,4 These large phase shifts, caused by nonresonant nonlinear index changes, are possible due to the combination of low nonlinear absorption, coupled with a localised enhancement related to the two-photon band edge.⁵ In addition, semiconductor waveguides are, in general, polarisation preserving. Taken together, these attributes make passive AlGaAs waveguides attractive alternatives for optical fibres in coupled-cavity lasers operating at wavelengths around 1.5 μm. In this paper, we describe the application of passive AlGaAs waveguides as the nonlinear element in a coupled-cavity KCl:TI colour-centre laser to produce pulses of less than 170 fs in duration. The principal advantage of using semiconductor waveguides over silica-based optical fibres is their low power requirement which offers considerable potential for miniaturisation.

© 1993 Optical Society of America